Orders over $75 ship free using a mix of UPS Ground and SurePost. Your order will arrive within 2-7 days, depending on your vicinity to Minneapolis. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. This offer is only available to the contiguous US. USPS shipments do not qualify for free shipping.

Fast flat-rate shipping $4.99

Select our $4.99 flat-rate shipping option, and your order will arrive to your door within 3 business days or less in the contiguous US. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. See map below for transit times.

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Quick Overview

Granular Ferric Oxide (GFO) removes phosphate from the aquarium and is one of the most commonly used filtration medias used in the aquarium industry. GFO is one of the few ways to easily maintain ultra low phosphate on a consistent basis. Maintaining these ultra low levels will help prevent algae outbreaks as well as treat existing algae issues. Your aquariums glass will also stay clear and free of the green hue significantly longer. GFO is most commonly used in a media reactor like the BRS reactor or media bag.

Phosphate inhibits proper coral growth by incorporating itself into the corals skeletal structure which makes it difficult for the coral to grow by laying down additional calcium and carbonate (alkalinity) ions. Maintaining ultra low phosphate levels will increase the growth of any SPS or LPS coral.

Algae outbreaks are one of the most common reasons for a complete tank shut down. We recommend preventing them by maintaining an ultra-low nutrient level environment where it would be difficult for them to get out of control to begin with. It is much easier to prevent outbreaks than it is to treat existing outbreaks.

Granular Ferric Oxide (GFO) removes phosphate from the aquarium and is one of the most commonly used filtration medias used in the aquarium industry. GFO is one of the few ways to easily maintain ultra low phosphate on a consistent basis. Maintaining these ultra low levels will help prevent algae outbreaks as well as treat existing algae issues. Your aquariums glass will also stay clear and free of the green hue significantly longer. GFO is most commonly used in a media reactor like the BRS reactor or media bag.

Phosphate inhibits proper coral growth by incorporating itself into the corals skeletal structure which makes it difficult for the coral to grow by laying down additional calcium and carbonate (alkalinity) ions. Maintaining ultra low phosphate levels will increase the growth of any SPS or LPS coral.

Algae outbreaks are one of the most common reasons for a complete tank shut down. We recommend preventing them by maintaining an ultra-low nutrient level environment where it would be difficult for them to get out of control to begin with. It is much easier to prevent outbreaks than it is to treat existing outbreaks.More

BRS Bulk GFO Granular Ferric Oxide

GFO comes in two types:

Granular GFO is varied in its shapes and requires the least amount of flow to tumble. Good for reactors.

High Capacity GFO is twice as dense as Granular GFO, so twice as much material will fit into a reactor. It's extremely hard and has less dust to begin with. Fewer fines will be created during use and transportation. By volume High Capacity GFO will remove roughly twice the phosphate compared to Granular GFO. Best overall performance.

Special note on fighting existing algae problems: Algae needs three main nutrients to grow: phosphate, nitrate and light. Reducing any one of these will significantly slow down algae growth but many not completely solve your issue. Once algae takes hold, it can be a difficult battle but it is winnable. The best offense against algae is to take preventative measures and attack before an outbreak is apparent. Use the following suggestions and be aggressive if an algae problem is already present:

Maintain undetectable phosphate levels with good feeding habits and use of a phosphate remover like GFO. 99% of all phosphate is added via foods added to the tank.

Control nitrate levels by reducing feedings, increasing the water change schedule and maintaining a properly sized protein skimmer.

Use nutrient free RO/DI water for water changes and top off water

Shorten your lighting period or intensity. In some cases aquarists have found replacing old bulbs that have fallen out of their intended spectrum helps as well

Continuously remove as much algae as possible by hand.

Add predators nothing helps an algae outbreak as much as critters who eat it all day long. Various tangs, lawn mower blennies, crabs and snails are all good options. It is also theorized that a healthy pod population will also control algae growth before it gets a chance to take root.

BRS Bulk GFO Granular Ferric Oxide

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Free economy shipping over $75

Orders over $75 ship free using a mix of UPS Ground and SurePost. Your order will arrive within 2-7 days, depending on your vicinity to Minneapolis. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. This offer is only available to the contiguous US. USPS shipments do not qualify for free shipping.

Fast flat-rate shipping $4.99

Select our $4.99 flat-rate shipping option, and your order will arrive to your door within 3 business days or less in the contiguous US. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. See map below for transit times.

No phosphateBy Michael on 7/29/2015

Michael would recommend this product to a friend

Had a problem starting with bubble algae and one problem area with turf algae. Ordered and used this in a BRS reactor SUPRISE no more algae and no phosphate. Works great, just use less than recommended at first so you don't shock your system. Takes about 3 gallons of RO to flush fines and rust color from the water. Ordered more when I ran out and will continue to use it.

good stuffBy johnny 5on 7/5/2015

johnny 5 would recommend this product to a friend

Saw significantly less hair algae after about 2 weeks. Works for me.

Best GFOBy Shawnon 7/4/2015

Shawn would recommend this product to a friend

One of the best ways to drop those nasty phoshate levels in a hurry. I honestly never tried another brand but I don't intend to if BRS keeps making quality GFO.

good stuffBy peter on 6/25/2015

peter would recommend this product to a friend

pretty good stuff. works as advertised.

Works greatBy Rayon 6/11/2015

Ray would recommend this product to a friend

Very important piece of the algae free puzzle.

Slightly larger pellets are awesome. By Turfon 6/7/2015

Turf would recommend this product to a friend

The slightly larger pellet size has made it substantially easier to deal with in a filter sock or reactor the ones I've used in the past.

5 stars hands downBy troyon 5/27/2015

troy would recommend this product to a friend

Easy to use rinse in ro di or with water change water and good to go

You know, Gfo.By Vegareef71on 5/24/2015

Vegareef71 would recommend this product to a friend

Brs Gfo is affective and very easy to use. Just follow the instructions on the container or hit up BRS online and the calculator with help you out.

Worth itBy Soseeon 5/21/2015

Sosee would recommend this product to a friend

a good value but don't use the amounts they recommend in the reactor. I followed the advice of a seasoned reefer and used half the recommended amount and it works great! Using too much can effect your alk levels.

greatBy wizon 5/20/2015

wiz would recommend this product to a friend

I'm assuming by my lack of green dlime and hair algae it has worked as promised. Thanks

It really does mean granular By Jameson 5/13/2015

James would recommend this product to a friend

I've only had the GFO in for about a week now but I've been testing every day (too much time on my hands) and my phosphate level is definitely on its way down. Not enough time yet to say anything about the algae, but science doesn't lie. I only have one thing, filter socks don't work with this. I put it in and started to rinse it out and it started coming out of the sock like dust (which it is). But that's my lack of experience, not the product.

A must for reefBy Deafclownon 5/6/2015

Deafclown would recommend this product to a friend

I wish I had used this in the beginning! I believe it's a must have for a reef to help keep phosphate down and calm the algae growth.

I want to mix GFO with carbon in the BRS single reactor. Is it OK to use the cheaper GFO to mix in with the carbon or do you need the high capacity GFO? I have a small system so I use low quantities of both carbon and GFO in my reactor. I was just worried about the regular GFO being too small.

Thanks,

James

Question by: James on Nov 19, 2013 7:22:00 AM

Hey James,
It doesn't cause any issues with the reactor to use standard GFO. Really the choice just comes down to the volume of space you have to work with. If you have a large tank you may need more regular GFO then will physically fit in the reactor. Then you either need to get a larger reactor, or use the HC GFO which only requires half the amount.

Sorry I didn't see the instructions, can you tell me how much I will neeed to use in your BRS reactor and how long between changeouts? I have a 90 gal tank and soon to be 125
thanks

Question by: Paul on Nov 27, 2013 10:19:00 AM

Hey Paul,
The easiest way to know is to use the reef calculator at the link below. You just enter the size of your tank and it will tell you how much to run. In the case of your 90g thats about 1.4 cups (22 tablespoons). How long it lasts depends on how much phosphates you add to the tank (which is largely a matter of how much you feed). Pretty typical is 4-6 weeks though.

Hi Ken,
The best way to know would be to test your water for phosphates using an easy to read phosphate meter like the hanna checker. When phosphates start to increase it would be a sign that the media is depleted and should be changed.

Is GFO the same thing as phosban ? Can it be used in two fishes reactor ? Should it tumble in the reactor? thanks

Question by: GH on Aug 4, 2014 3:51:00 PM

GFO is Granular Ferric Oxide, it is the name of the actual material. Phosban happens to be just a brand name of a GFO product (among others). It can certainly be used in a phosban reactor and you do want to tumble it or it will clump together into a big rock.

Hi Jason,
It wouldn't be likely to see any negative effect on your calcium or alkalinity. Its worth noting though, phosphate prevents precipitation (for example the formation of coral skeletons), so by removing phosphates your corals can grow easier which would mean they consume more calcium and alkalinity.

Hey Michael,
GFO should be changed when it is depleted. How long this takes will depend on the amount of phosphate that is added to the tank. A pretty typical tank that would usually be 4-6 weeks or so but the best way to tell is to monitor the phosphates. When they start to increase that would indicate that DI resin has reached its capacity.

starting a 90 gallon . will also buy your reactor , how much product do I need to start out to fill the reactor. Thank John

Question by: John Lasky on Mar 1, 2014 11:28:00 AM

Hi John,
The amount of media depends on the size of your tank with the maximum capacity of the reactor being 2 cups of media, though fortunately with your size tank you wouldn't be in excess of that. For a 90g tank you would use 1.5 cups of media. The easiest way to get measurements for most of these products is to use the BRS Calculator which can be found right here:

I have a biocube 29 and was wondering if this product can be used with some sort of a bag hanging in one of the back chambers of my tank? Will that be effective. I do not have the space or the recources to get a reactor.

Thanks,

John

Question by: John on Apr 6, 2014 11:05:00 AM

Hi John,
It won't be as effective as a reactor and you will want to periodically knead the bag, but it would certainly be better then nothing.

How long should the GFO remain in the reactor? The fake stuff at the stores say 7 hours. Thank you for your time.

Question by: Jason on May 11, 2014 7:59:00 AM

Hey Jason,
It depends on how much phosphates you have. The more you have, the faster it will need to be replaced and vice versa. As a whole though 4-6 weeks would be pretty typical. The best thing to do would be to monitor your phosphate levels with something like a Hanna phosphate checker. When the phosphates begin to rise that would indicate your GFO is used up and its time to change it.

Granular GFO is varied in its shapes and requires the least amount of flow to tumble. Good for reactors.

High Capacity GFO is twice as dense as Granular GFO, so twice as much material will fit into a reactor. It's extremely hard and has less dust to begin with. Fewer fines will be created during use and transportation. By volume High Capacity GFO will remove roughly twice the phosphate compared to Granular GFO. Best overall performance.

Special note on fighting existing algae problems: Algae needs three main nutrients to grow: phosphate, nitrate and light. Reducing any one of these will significantly slow down algae growth but many not completely solve your issue. Once algae takes hold, it can be a difficult battle but it is winnable. The best offense against algae is to take preventative measures and attack before an outbreak is apparent. Use the following suggestions and be aggressive if an algae problem is already present:

Maintain undetectable phosphate levels with good feeding habits and use of a phosphate remover like GFO. 99% of all phosphate is added via foods added to the tank.

Control nitrate levels by reducing feedings, increasing the water change schedule and maintaining a properly sized protein skimmer.

Use nutrient free RO/DI water for water changes and top off water

Shorten your lighting period or intensity. In some cases aquarists have found replacing old bulbs that have fallen out of their intended spectrum helps as well

Continuously remove as much algae as possible by hand.

Add predators nothing helps an algae outbreak as much as critters who eat it all day long. Various tangs, lawn mower blennies, crabs and snails are all good options. It is also theorized that a healthy pod population will also control algae growth before it gets a chance to take root.

I want to mix GFO with carbon in the BRS single reactor. Is it OK to use the cheaper GFO to mix in with the carbon or do you need the high capacity GFO? I have a small system so I use low quantities of both carbon and GFO in my reactor. I was just worried about the regular GFO being too small.

Thanks,

James

Question by: James on Nov 19, 2013 7:22:00 AM

Hey James,
It doesn't cause any issues with the reactor to use standard GFO. Really the choice just comes down to the volume of space you have to work with. If you have a large tank you may need more regular GFO then will physically fit in the reactor. Then you either need to get a larger reactor, or use the HC GFO which only requires half the amount.

Sorry I didn't see the instructions, can you tell me how much I will neeed to use in your BRS reactor and how long between changeouts? I have a 90 gal tank and soon to be 125
thanks

Question by: Paul on Nov 27, 2013 10:19:00 AM

Hey Paul,
The easiest way to know is to use the reef calculator at the link below. You just enter the size of your tank and it will tell you how much to run. In the case of your 90g thats about 1.4 cups (22 tablespoons). How long it lasts depends on how much phosphates you add to the tank (which is largely a matter of how much you feed). Pretty typical is 4-6 weeks though.

Hi Ken,
The best way to know would be to test your water for phosphates using an easy to read phosphate meter like the hanna checker. When phosphates start to increase it would be a sign that the media is depleted and should be changed.

Is GFO the same thing as phosban ? Can it be used in two fishes reactor ? Should it tumble in the reactor? thanks

Question by: GH on Aug 4, 2014 3:51:00 PM

GFO is Granular Ferric Oxide, it is the name of the actual material. Phosban happens to be just a brand name of a GFO product (among others). It can certainly be used in a phosban reactor and you do want to tumble it or it will clump together into a big rock.

Hi Jason,
It wouldn't be likely to see any negative effect on your calcium or alkalinity. Its worth noting though, phosphate prevents precipitation (for example the formation of coral skeletons), so by removing phosphates your corals can grow easier which would mean they consume more calcium and alkalinity.

Hey Michael,
GFO should be changed when it is depleted. How long this takes will depend on the amount of phosphate that is added to the tank. A pretty typical tank that would usually be 4-6 weeks or so but the best way to tell is to monitor the phosphates. When they start to increase that would indicate that DI resin has reached its capacity.

starting a 90 gallon . will also buy your reactor , how much product do I need to start out to fill the reactor. Thank John

Question by: John Lasky on Mar 1, 2014 11:28:00 AM

Hi John,
The amount of media depends on the size of your tank with the maximum capacity of the reactor being 2 cups of media, though fortunately with your size tank you wouldn't be in excess of that. For a 90g tank you would use 1.5 cups of media. The easiest way to get measurements for most of these products is to use the BRS Calculator which can be found right here:

I have a biocube 29 and was wondering if this product can be used with some sort of a bag hanging in one of the back chambers of my tank? Will that be effective. I do not have the space or the recources to get a reactor.

Thanks,

John

Question by: John on Apr 6, 2014 11:05:00 AM

Hi John,
It won't be as effective as a reactor and you will want to periodically knead the bag, but it would certainly be better then nothing.

How long should the GFO remain in the reactor? The fake stuff at the stores say 7 hours. Thank you for your time.

Question by: Jason on May 11, 2014 7:59:00 AM

Hey Jason,
It depends on how much phosphates you have. The more you have, the faster it will need to be replaced and vice versa. As a whole though 4-6 weeks would be pretty typical. The best thing to do would be to monitor your phosphate levels with something like a Hanna phosphate checker. When the phosphates begin to rise that would indicate your GFO is used up and its time to change it.

Full Details

GFO comes in two types:

Granular GFO is varied in its shapes and requires the least amount of flow to tumble. Good for reactors.

High Capacity GFO is twice as dense as Granular GFO, so twice as much material will fit into a reactor. It's extremely hard and has less dust to begin with. Fewer fines will be created during use and transportation. By volume High Capacity GFO will remove roughly twice the phosphate compared to Granular GFO. Best overall performance.

Special note on fighting existing algae problems: Algae needs three main nutrients to grow: phosphate, nitrate and light. Reducing any one of these will significantly slow down algae growth but many not completely solve your issue. Once algae takes hold, it can be a difficult battle but it is winnable. The best offense against algae is to take preventative measures and attack before an outbreak is apparent. Use the following suggestions and be aggressive if an algae problem is already present:

Maintain undetectable phosphate levels with good feeding habits and use of a phosphate remover like GFO. 99% of all phosphate is added via foods added to the tank.

Control nitrate levels by reducing feedings, increasing the water change schedule and maintaining a properly sized protein skimmer.

Use nutrient free RO/DI water for water changes and top off water

Shorten your lighting period or intensity. In some cases aquarists have found replacing old bulbs that have fallen out of their intended spectrum helps as well

Continuously remove as much algae as possible by hand.

Add predators nothing helps an algae outbreak as much as critters who eat it all day long. Various tangs, lawn mower blennies, crabs and snails are all good options. It is also theorized that a healthy pod population will also control algae growth before it gets a chance to take root.

Reviews

No phosphateBy Michael on 7/29/2015

Michael would recommend this product to a friend

Had a problem starting with bubble algae and one problem area with turf algae. Ordered and used this in a BRS reactor SUPRISE no more algae and no phosphate. Works great, just use less than recommended at first so you don't shock your system. Takes about 3 gallons of RO to flush fines and rust color from the water. Ordered more when I ran out and will continue to use it.

good stuffBy johnny 5on 7/5/2015

johnny 5 would recommend this product to a friend

Saw significantly less hair algae after about 2 weeks. Works for me.

Best GFOBy Shawnon 7/4/2015

Shawn would recommend this product to a friend

One of the best ways to drop those nasty phoshate levels in a hurry. I honestly never tried another brand but I don't intend to if BRS keeps making quality GFO.

good stuffBy peter on 6/25/2015

peter would recommend this product to a friend

pretty good stuff. works as advertised.

Works greatBy Rayon 6/11/2015

Ray would recommend this product to a friend

Very important piece of the algae free puzzle.

Slightly larger pellets are awesome. By Turfon 6/7/2015

Turf would recommend this product to a friend

The slightly larger pellet size has made it substantially easier to deal with in a filter sock or reactor the ones I've used in the past.

5 stars hands downBy troyon 5/27/2015

troy would recommend this product to a friend

Easy to use rinse in ro di or with water change water and good to go

You know, Gfo.By Vegareef71on 5/24/2015

Vegareef71 would recommend this product to a friend

Brs Gfo is affective and very easy to use. Just follow the instructions on the container or hit up BRS online and the calculator with help you out.

Worth itBy Soseeon 5/21/2015

Sosee would recommend this product to a friend

a good value but don't use the amounts they recommend in the reactor. I followed the advice of a seasoned reefer and used half the recommended amount and it works great! Using too much can effect your alk levels.

greatBy wizon 5/20/2015

wiz would recommend this product to a friend

I'm assuming by my lack of green dlime and hair algae it has worked as promised. Thanks

It really does mean granular By Jameson 5/13/2015

James would recommend this product to a friend

I've only had the GFO in for about a week now but I've been testing every day (too much time on my hands) and my phosphate level is definitely on its way down. Not enough time yet to say anything about the algae, but science doesn't lie. I only have one thing, filter socks don't work with this. I put it in and started to rinse it out and it started coming out of the sock like dust (which it is). But that's my lack of experience, not the product.

A must for reefBy Deafclownon 5/6/2015

Deafclown would recommend this product to a friend

I wish I had used this in the beginning! I believe it's a must have for a reef to help keep phosphate down and calm the algae growth.

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